This invention relates to a control apparatus for controlling, for example, equipment for manufacturing semiconductor devices.
In the photolithography process in the manufacture of semiconductor devices, after the photoresist coating process of forming a photoresist film on the surface of a semiconductor wafer (hereinafter, referred to as a wafer) and the exposure process of exposing the resist-coated wafer have been carried out, the development process of developing the exposed wafer is performed. The photoresist coating process and the development process are carried out according to a specific sequence in a complex processing system constructed by various processing units, as disclosed in, for example, Jpn. Pat. Appln. KOKOKU Publication No. 2-30194.
In sequence control in such a system, software bugs or hardware problems can cause the system to go down. Should this happen, it is necessary to investigate the causes of the malfunction. Jpn. Pat. Appln. KOKAI Publication No. 5-324053 has disclosed the technique for causing a data collector to constantly acquire the data from a sequence controller and, when a failure has occurred in an automatic machine, displaying the acquired data covering a certain point in time to the time when the failure occurred on a data history display. This enables the operator to learn the cause of the malfunction from the displayed acquired data.
In ordinary sequence control, the volume of the acquired data is often enormous. In a complex processing system including the aforementioned processing units, various types of control are performed and therefore the volume of the acquired data is tremendous. Accordingly, it is very difficult to find out the cause of the malfunction from the displayed acquired data.
To overcome this problem, for example, Jpn. Pat. Appln. KOKAI Publication No. 5-324053 has disclosed the technique for storing the normal data beforehand in the system and extracting the cause of the malfunction by comparing the normal data with the acquired data.
The volume of the normal data increases as the volume of the acquire data increases and therefore the former is often enormous. As a result, particularly in the case of the complex processing system, the following problem arises: storing such an enormous amount of normal data requires memory means with a tremendous memory capacity.